A quality that can only be described by a number (magnitude) is called what?

A quality that can only be described by a number (magnitude) is defined as a scalar. Scalars are quantities that have magnitude but no direction. Examples of scalar quantities include temperature, mass, time, and speed. These quantities can be fully described with just a numerical value and a unit, without any indication of direction.

In contrast, other types of quantities like vectors include both magnitude and direction. For instance, velocity has both a speed (magnitude) and a direction (like north or east). Understanding the distinction between scalars and vectors is fundamental in fields such as physics and chemistry, where different types of measurements are critical for accurate analysis and problem-solving.

Thus, the classification of a quality that can solely be described by a number as a scalar is accurate and aligns with the definitions commonly used in scientific contexts.